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I think they turned whatever is causing it off. I doubt it has anything to do with internals or power, just chip set-up (which is probably shooting in the dark, not sure how much detailed information manufacturers get from ESS). But Oppo seems to have pulled it off!

Senior Member

Amir, thanks again for this great review!
That DAC is a very good surprise, for once!

There is something I don't quite understand there though: the jitter measurement shows a very low nosie floor, yet the DNR is not that good.
The Gala DAC was in the opposite situation, with an apparent higher noise floor in the jitter test, yet a very good DNR.
How is this possible? Does the noise floor rises significantly above 20kHz in the case of the Khadas?
Maybe an A-weighted DNR measurement would be more representative here.

Senior Member

Amir, could you please run a few tests with the spdif input? (jitter, and maybe SINAD and DNR if you feel like they might be impacted)
All this with a generic switcher power supply on the USB port please

Major Contributor

Amir, thanks again for this great review!
That DAC is a very good surprise, for once!

There is something I don't quite understand there though: the jitter measurement shows a very low nosie floor, yet the DNR is not that good.
The Gala DAC was in the opposite situation, with an apparent higher noise floor in the jitter test, yet a very good DNR.
How is this possible? Does the noise floor rises significantly above 20kHz in the case of the Khadas?

Active Member

It is nice to see a great performer at this price range, but something tells me that all of these Chinese DACs might be based on the same reference design. All three of D50, SU-8 and Khadas DAC have the same DAC chip (ESS9038Q2M), USB chip (XMOS XU208) and similar level of performance. Both SU-8 and D50 use OPA1612 opamps and I wouldn't be surprised if this DAC has the exact same opamp as those 2, which might have something to do with the hump on IMD tests. Allo Katana also uses the same DAC chip but doesn't have this issue.

Major Contributor

They might not be designed on the same reference design no, performance tends to vary greatly.

There just are a lot of often recurring 'staple' components in these Chinese products. XMOS interface and ESS dac chip are just about expected, the use of Japanese AKM chips is already becoming more rare, and Savitech or C-Media interfaces seem just about never used. I expect Chinese chips are just that much cheaper to work with, even cheaper when sourced and manufactured in China. Kinda makes sense, no.

Active Member

Okay that's fair but how do you explain the hump then? All the DACs that use this particular ES9038Q2M + OPA1612 config that get measured here (DX7s, D50, SU-8 and most likely Khadas too) are all Chinese products and they all have the hump. I don't think it is related to ES9038Q2M because the other 2 measured DACs (Allo Katana and Pro-ject Pre S2) that use the same chip don't have that issue.

Major Contributor

Okay that's fair but how do you explain the hump then? All the DACs that use this particular ES9038Q2M + OPA1612 config that get measured here (DX7s, D50, SU-8 and most likely Khadas too) are all Chinese products and they all have the hump. I don't think it is related to ES9038Q2M because the other 2 measured DACs (Allo Katana and Pro-ject Pre S2) that use the same chip don't have that issue.

@amirm, since this hump is such a common (although not ubiquitous) feature of devices using this ESS chip, I'd find it interesting to see a distortion spectrum in the range of the hump, say at around -25 to -30dB, to compare to the spectrum at 0dBfs.

Don't know if you have time, but it'd be interesting to see spectra of:

THD @ -30dBfs (to compare to THD @ 0dBfs)

IMD @ 0dBfs

IMD @ -30dBfs

Or something along these lines....

Also, since the hump gets discussed in every thread every time it is measured, maybe a new thread could be started to explain what causes it? It could then just be linked every time it comes up in the measurements.

Member

but something tells me that all of these Chinese DACs might be based on the same reference design. All three of D50, SU-8 and Khadas DAC have the same DAC chip (ESS9038Q2M), USB chip (XMOS XU208) and similar level of performance. .

Khadas Tone Board is only one model from Khadas Family, and we suggest user could buy Khadas Tone Board along with the Khadas VIMs for SPDIF in/out can enjoy high resolution audio and 4K video together. That we need to consider the compabilty of Khadas Tone Board and Khadas VIM Boards. Through Khadas Docs, you could get the user manual along with the below details:

Active Member

Khadas Tone Board is only one model from Khadas Family, and we suggest user could buy Khadas Tone Board along with the Khadas VIMs for SPDIF in/out can enjoy high resolution audio and 4K video together. That we need to consider the compabilty of Khadas Tone Board and Khadas VIM Boards. Through Khadas Docs, you could get the user manual along with the below details:

Major Contributor

This is all great honestly. Thinking about buying the board and the DIY enclosure they sell.
My only complaint is the dual usb-c power/data line which is at the same time both a great modern convenience but also not as flexible.

Anyone else has plans for putting it in some enclosure that is fancier/sexier than the one they sell?

Active Member

This is all great honestly. Thinking about buying the board and the DIY enclosure they sell.
My only complaint is the dual usb-c power/data line which is at the same time both a great modern convenience but also not as flexible.

Anyone else has plans for putting it in some enclosure that is fancier/sexier than the one they sell?